1. Field of the Invention
The present invention relates to a call service control method in a digital switching system, and more particularly to a method for controlling an automatic attendant voice paging service in a digital switching system.
2. Description of the Related Art
In a switching system such as a private exchange or key telephone system, an automatic attendant function is provided. In accordance with such an automatic attendant function, an off-hook is automatically carried out in a switching system in response to an incoming ring from a central office line, thereby establishing a terminating channel. A voice announcement from the switching system is then transferred to a caller. If necessary, the voice announcement, which is stored in an automatic answering machine equipped in the switching system, may be optionally changed by the operator of the switching system. Thus, such a message for an automatic answering can be appropriately set in accordance with the characteristics of the switching system. In accordance with the voice announcement, the caller at the site of the central office line dials a desired extension number and a desired extension group number so that he can talk with a desired extension subscriber. The automatic attendant function, which is stored in an automatic attendant function card equipped in the switching system, is an edit-type voice announcement function. In accordance with such an edit-type voice announcement function, avariety of basic sentences are previously stored in the form of recorded voices. In accordance with a given situation, appropriate basic sentences are edited into a complete sentence which is, in turn, transferred as an announcement message. In a switching system having the above-mentioned automatic attendant function, it is possible to achieve a service associated with an incoming call signal from a central office line in accordance with a voice announcement without using any telephone operator.
In accordance with an automatic attendant service adopted in a conventional switching system having the above-mentioned automatic attendant function, an off-hook is first automatically carried out in the switching system in response to an incoming ring from a central office line, thereby establishing a terminating channel. The switching system then carries out a voice announcement function, thereby advising a caller at the side of the central office line of information about extension subscribers. When the caller dials a desired extension number and a desired extension group number in accordance with the voice announcement, the switching system senses the dialing and then sends a ring signal to a desired extension subscriber.
That is, when the switching system receives dialing information about a desired extension number, it sends a ring signal to a desired extension subscriber. Where the extension subscriber performs an off-hook in response to the ring signal, the switching system executes a call service function associated with an incoming call from the central office line. Where there is no response to the ring signal due to an absence of the extension subscriber or other reasons, one of other extension subscribers should respond to the incoming call signal and then execute a switching function. On the other hand, where the caller at the site of the central office line dials only the number of a desired extension group, one of extension subscribers belonging to the extension group carries out a call conversation in response to the ring signal and then switches the incoming call to a desired extension subscriber in accordance with an appropriate method.
Accordingly, the automatic attendant function used in the conventional switching system requires an extension subscriber capable of executing the function of a telephone operator or a switching function. In this case, however, a degradation in the efficiency of the automatic answering machine, which is expensive, occurs.